The present invention relates to footwear, in particular to boots, and therefore henceforth referred to in this specification as boots, to be used in conjunction with anti-g suits of the type used by crew members of highly manoeuvrable agile aircraft such as fighters. The effect of positive acceleration- commonly referred to as +Gz- in the "z" plane (that is in the plane along the length of the body of an erectly seated crew member) when an aircraft is manoeuvring is to prevent blood from returning to the heart, resulting in the pooling of blood in legs and feet and a reduction in blood supply to the brain. The reduction in blood supply to the brain causes a progressive loss of visual acuity, unconsciousness and, if the g is not reduced, death.

A common method of reducing and delaying the effects of +Gz is the wearing of "anti- g trousers", which have bladders to apply pressure to the major areas of muscle on the lower torso and legs, thereby reducing the rate at which blood drains downward. Pressurised gas is supplied to the bladders from a supply controlled by a +Gz sensitive switch. These trousers leave the feet unprotected, and as the degree of protection afforded by anti- g trousers, leading to the presently used "Full Cover Anti-G Trousers", has increased, this has caused the blood to become even more trapped in the feet causing pain and, in extreme cases, petechial haemorrhaging of the feet.

According to one aspect of the present invention a boot has uppers having a lining covering, in use, a substantial area of an upper foot, the lining being inflatable and including means whereby it can be connected to a pressurisation supply.

According to another aspect of the invention an aircraft anti-g system includes a boot having a lining covering a substantial area of a wearer's upper foot, the lining being inflatable and being connected to a pressurisation supply controlled by a g- sensitive switch.

The pressurisation supply may be obtained directly, usually from the same supply as that for anti-g trousers used in the system, or indirectly via a connection to such anti-g trousers. However it might in some cases be advantageous to use different pressurisation for boots and for trousers.

The exterior footwear normally used by aircrew of fighter aircraft must be practical walking footwear, and usually comprises leather boots which cover the ankles. The boots usually have uppers with a tough leather outer layer and a fine leather inner layer. The inflatable lining can advantageously be positioned between the two layers of such boots.

The lining is preferably provided by a preformed bladder shaped to be conformable with an inner surface of the boot to which it is attached during manufacture. The bladder may be formed of a single item or of a plurality of items joined together. A suitable material for the bladder is Polyurethane (PU) coated Nylon mesh material, although other materials, such as, for example, weldable PU, a Nylon/ Butyl/ Nylon laminate or Butyl coated Rip-stop Nylon might be used. The means for connecting the inflatable lining to the pressurisation system preferably includes a port in the lining which penetrates the outer layer of the boot and which can be connected to the lower leg portion of the anti- g trousers by small bore rubber hose and a detachable connector.

Use of the invention involves the user in little more effort in dressing than when dressing in normal anti- g trousers. Early attempts at providing anti- g protection for feet involved the use of inflatable bladders that were wrapped round the feet, or which were in the form of socks. Both of these methods involved permanent attachment to the trouser leg ends to form extensions to the main bladder.

It will be realised, of course, that boots according to the invention differ in both intention and operation from the known "inflatable" training footwear. In this known footwear the sole or the tongue thereof can be inflated to a required degree by the user, but the degree of inflation cannot be adjusted during continuous use. There are known boots where a degree of pressurisation can be applied to the ankle area to improve the fitting of the boot around the ankle, although for comfort the pressurisation must not be such as to restrict the flow of blood to the foot. In neither of these types of prior art footwear does the degree of inflation affect the pressures exerted on a foot within the footwear.

Some embodiments of the invention will now be described, by way

of example only, with reference to the accompanying diagrammatic drawings, of which:

Figure 1 is an elevation, in section, of a boot according to the invention,

5 Figures 2a and 2b show the components of the inflatable lining of the boot of Figure 1, and

Figures 3a. 3b and 3c, and 4a, 4b and 4c show components and constructions for two other types of inflatable lining.

A boot 10 according to the invention (Figure 1) has a sole 11

10 and upper 12, both shown in dotted lines, and an inflatable inner lining 13 for the area of boot which will cover the upper part of a wearer's foot. An inflation port 14 in the inner lining 13 is secured to a tube 15 which projects outwardly from the boot 10.

The inner lining 13 is formed from two bladders, a rear bladder

15 16 (Figure 2a) and a front bladder 17 (Figure 2b), the front bladder 17 having a body portion 18 and a tongue portion 19. The bladders 16, 17 may be formed, for example, from two sheets configured as illustrated in figures 2a and 2b welded or glued together at the edges. The bladders 16 and 17 are united to form the inflatable

20 lining 13 by joining ends 20a, 21a of the rear bladder 16 respectively to ends 20b, 21b of the front bladder 17 to give joints 22 (see Figure 1). Joining may be effected by, for example, glue and tape or welding, there being a connection between the interiors of bladders 16 and 17 at at least one of the joints 22.

25 In use the boot 10 is donned by a wearer and the tube 15 is connected to a source of pressurisation, for example the gas supply used for pressurising anti-g trousers used by the wearer, the connection preferably being to the trouser bladder. As the wearer is subjected to g forces the g is detected by means well known to those

30 in the art and gas under pressure is supplied by -means also well known to those in the art to pressurise the anti-g trousers and also the inflatable lining 13 of the boot 10. The inflatable lining then, on inflation, takes up the space between the outer leather of the boot and the foot of the wearer and bears with an even pressure on the

35 ankle and upper surface of the wearer's foot, and on the surface blood vessels. The sole of the foot is pressed firmly to the sole of the boot by the same mechanism.

It will be realised that the tube 15 may be connected to the anti-g trousers or directly to the pressurisation supply. There may also be occasions where it is considered advantageous to connect the boot 10 to a pressurisation supply at a different pressure to that supplied to the anti-g trousers.

Alternative forms of bladders used to form the inner lining 13 are illustrated in Figures 3a, 3b and 3c, and in Figures 4a, 4b and 4c.

In Figures 3a, 3b and 3c items corresponding to items 16 to 22 are numbered 36 to 42.

In Figures 4a, 4b and 4c A single bladder 46 has ends 4θa, 4θb joined at joint 2 to form both rear and front portions of the inflatable lining 13, and a stub 48 of the bladder 46 has an end 4θa secured to an end 4lb of a tongue bladder 47. the joint, 53. being such as to interconnect the bladders.

It will, of course, be realised that many alternative forms of boot 10 and of inflatable lining 13 are possible within the scope of the invention. For example alternative ways of forming an inflatable lining 13 are possible, including the use of single bladder. Also it will be realised that whilst the boot 10 has been described above as having an upper 12 comprising a single layer of material, this is for ease of description. More usually a boot upper 12, typically in a boot 10 as worn by aircrew, will comprise at least an outer tough layer and an inner flexible layer. The inflatable lining 13 can then conveniently be positioned between these layers.